1. Field of the Invention
This invention relates to a cyclone separation apparatus.
2. Related Background Art
Cyclonic separation apparatus are well known apparatus for removing particles from a gas flow without the use of filters. Cyclone separators have found utility in the field of vacuum cleaners to separate dirt and dust from the airflow. It is well known that the separation efficiency of cyclonic separators is dependent upon the force which is applied to the particles in the airflow, in accordance with the following formula:F=2mv2/d, where    F=the force applied to the particles;    m=the mass of the particle;    v=the flow velocity; and,    d=the diameter of the cyclonic air flow
Thus, it is evident that the separation efficiency is inversely proportional to the diameter of the cyclone chamber, such that smaller diameter cyclones are more suited to separating lighter particles than larger diameter cyclones. Accordingly, it is well known for vacuum cleaners to incorporate a first upstream separation stage, comprising a relatively large diameter cyclone and a plurality of parallel connected downstream cyclones having a smaller diameter. In use, the upstream cyclone separates coarse dirt and dust from the airflow, whereas the downstream cyclones separate the finer dirt and dust.
Cyclonic separators for vacuum cleaners comprising two stages of separation have been proposed. U.S. Pat. No. 2,171,248 discloses an arrangement whereby a high efficiency downstream cyclone is nested co-axially inside a low efficiency upstream cyclone. The respective cyclones discharge their separated solid material into a removable receptacle comprising a central chamber for the material discharged from the downstream cyclonic chamber, and an annular chamber from material discharged from the upstream cyclonic chamber.
EP1674021 discloses a two stage cyclonic separator for a vacuum cleaner comprising a low efficiency upstream cyclone separator, followed by an array of parallel-connected mini cyclones disposed in an annular chamber, which surrounds the first cyclonic chamber. Partly cleaned air that exits first stage passes upwards by way of an axially orientated central outlet and is fed into the high efficiency cyclones. However, the complex alignment of the flow path between the two stages of the separation gives rise to a pressure drop.
DE 202006017010 discloses a two stage cyclonic separator for a vacuum cleaner again comprising a low efficiency cyclone separator followed by an array of parallel connected high efficiency cyclone separators situated above the first stage. Partly cleaned air leaving the first stage is ducted upwards through an annual cavity between the high efficiency cyclones and the outer wall of the separator unit and is then ducted regularly inwards to the respective high efficiency cyclones. This arrangement gives rise to less of a pressure drop. However, in situations where the high efficiency cyclones are not disposed equidistantly on the periphery of the separator unit, the cyclones can become unevenly loaded with respect to the dust laden air, and can result in the blocking of some cyclones.